Heretofore, ships such as bulk carriers and tankers include a large-sized diesel engine (main engine) to obtain propulsive power and a middle-sized diesel engine (auxiliary engine) as an electric generator to generate electric power for onboard electric power sources and the like. In recent years, there has been a demand for these types of ships to achieve energy saving and reduction in the amount of fuel consumption in view of problems such as the rising price of fossil fuel and the emission control. For example, a method is disclosed in which when a ship is berthing at a quay for cargo handling, regenerative energy of a crane performing cargo handling at the dock or the like is supplied as the ship's onboard electric power (see Patent Document 1, for example). This configuration allows the ship to reduce the amount of fuel consumption by an electric generator and the like during berthing.
Moreover, a method is disclosed in which a ship receives electricity as its onboard electric power from a land power supplying facility through a land power receiving facility installed on the ship (see Patent Document 2, for example). In this case, these facilities can cover the whole electric power required by the ship during berthing.
However, the ship described above has a problem of requiring the same amount of energy (such as fossil fuel) as conventional cases during navigation. That is, improvement is yet to be made to the amount of exhaust emission, the amount of fossil fuel consumption, and the like while the ship is on the ocean.